This triangular pyramid is a type II as the book puts it. Three faces are right triangles and the 4th in a diagonal plane is an oblique triangle. The book explaines that if the angle to be found is in the oblique triangle you should solve for an auxilliary angle in the third right angle which lies at the same vertex as the required angle, thus spliting the pyramid into two parts. I need help constructing the auxilliary angle.
The problem is to solve Beta with one face angle at 25 degrees and Theta which is 22 degrees.
An auxilliary angle in a type II pyramid is calculated.